Voters head to polls in three NSW seats

Voters in three NSW electorates are heading to the polls, with the Liberal party bracing for huge swings against it in some of its safest seats.

Gladys Berejiklian, who's facing her first litmus test as NSW premier, says she believes each poll will go down to the wire.

The seats of Manly and North Shore in northern Sydney are up for grabs, while voters will also take to the polls for the seat of Gosford on the state's Central Coast on Saturday following the resignation of local MPs, including former premier Mike Baird.

The Liberals hold Manly by 24.5 percent on a two-party preferred basis while former health minister Jillian Skinner won North Shore on a 21.2 percent margin in 2015.

Anger over the state government's controversial council amalgamations policy is expected to hurt the Liberal party vote in the North Shore, where a number of independent candidates including anti-merger Mosman councillor Carolyn Corrigan are campaigning against it.

She's among six hopefuls, along with recently gaffe-prone Liberals candidate Felicity Wilson, vying for the blue-ribbon electorate.

Further north in Manly, a dozen candidates are in the running to fill the safe Liberal seat vacated after Mr Baird decided to quit public life.